Transcranial magnetic stimulation (TMS) is a non-invasive method for stimulating or inhibiting of neuronal networks in the brain. Besides brain research, it is also used for therapeutic treatment for example of depression.
The correct and reproducible positioning of a magnetic coil used in this process on the head of the patient is one of the most important requirements of TMS. Individual stimulation points, so-called hot spots, have to be identified for each patient and have to be found once again for each session. The stimulation coil has to be positioned at the desired stimulation point and remain continuously in this position during a session. To relieve the neck of the patient during the sessions, either a vacuum cushion for relaxed positioning of the head or a patient armchair with an integrated headrest is used.
In everyday clinical practice, hats or bathing caps, on which the individual stimulation points of a patient are marked, are mostly used. To determine a suitable stimulation point and a suitable stimulation intensity, the head is measured and possible stimulation points (a so-called 9-point grid) are marked. Then, the brain area that represents the hand function in the brain is sought based on the marked grid through emission of stimulation pulses with sufficient intensity and an appropriate orientation of the coil. During stimulation of the right place with sufficient intensity, the reaction of the thumb is measured. The point with the best reaction is marked on the cap. The individual stimulation intensity is measured here, and this point serves in addition as a starting point for measuring and marking of the individual therapy point (e.g. by means of the 5 cm rule). This individually measured therapy point is marked on the cap and used as a place of stimulation for each session. The positioning of the coil has to be ensured during treatment through holding of the coil or through clamping into a holding device. Fixation and/or support of the head is not taken into account in this process and can be ensured separately, e.g. through a vacuum cushion or an appropriate neckrest on the patient armchair. This method is very easy to learn and a cost-efficient solution. However, the stimulation points cannot be found once again with a 100% accuracy because the cap cannot be put on in exactly the same way for a second time. In addition, the head of the patient must not move during stimulation and the coil has to be held in a way that it will not change the position on the head for the period of stimulation.
Further, the use of coil positioning systems in which the coil is positioned in relation to the head on the basis of holding and measurement tools is known. In these systems, the patient must not change the position of the head during stimulation because the coil positioning systems cannot follow the movement of the head and/or the contact of the coil to the head is measured by means of a sensor and because stimulation is stopped when the coil loses con-tact with the head (e.g. due to a head movement). In addition, a special patient armchair, which supports the head of the patient during stimulation, has to be used when this method is applied.
Neuro-navigation systems can be used for high-precision positioning of the coil. Said systems use MRT photographs of the respective patient in order to create a three-dimensional model of the head and the brain. By means of ultrasound or infrared tracking systems, the positions of the coil and the head/brain in relation to one another are determined in real time and displayed in the 3D model. With this, the coil can be positioned very easily over the area to be stimulated and the position of the coil can be saved. Although finding of the right stimulation point through neuro-navigation is not necessarily facilitated (the therapy point has to be measured manually as in case of using the caps), this method offers very good reproducibility and a documentation possibility of the stimulation point as soon as said stimulation point is determined thanks to diverse memory possibilities of the coil-head coordinates. However, also in this method both the coil, which is held manually or by means of a holding system, as well as the head of the patient have to be held steady during the entire stimulation period as the stimulation position will otherwise be left. In addition, the costs for purchasing such a sys-tem are very high. Furthermore, the user has to be trained on the use of computers, software and navigation systems.
A relatively new development is a TMS robot as a type of intelligent coil holder that holds the coil automatically in the position marked in the navigation in relation to the head of the patient by means of a neuro-navigation system and that guides it along in case of a movement of the patient. The TMS robot can move the coil in three or more directions and therefore can ensure in connection with a sensor the respective positioning and the contact of the coil to the head. The large space, technology and training requirement to operate the expensive robot is disadvantageous.
A positioning system for navigated transcranial magnetic stimulation is known from DE 102 42 542 A1. The positioning system comprises a support bar as a holder for a bracket on which a second bracket is fastened via two rotary suspension devices and in a way that it can be swiveled around a swivel axis. A trolley is disposed on the second bracket in a motor-driven way. The stimulation coil is fastened on the trolley by means of a motor-driven adjustment possibility. By means of motor-driven swiveling of the second bracket around the swivel axis, motor-driven movement of the trolley along the second bracket and motor-driven adjustment of the adjustment possibility on the trolley, the position of the stimulation coil can be adjusted in relation to the head of a patient. In addition, a support for the head of the patient is fastened on the support bar. To keep the head of the patient in a fixed place, the support has fastening elements in form of a belt that is strapped around the forehead of the patient and presses the head of said patient onto the support in a way as to fix it. Alternatively, supports with additional form- and/or force-fitting clamping devices or clampings for the patient's head should be provided. By installing the support as a fixation of the patient's head on the support bar, patient movements should be reduced. The support bar can for example be installed on a seat for the patient. Neither the support for the head nor the fixation elements for fixing the head on the support should limit the patient's field of vision. The treatment can still be unpleasant for the patient because his head must not and cannot be moved during adjustment of the position of the stimulation coil as well as during the entire treatment. In particular in case of repeated treatment, this can lead to tensions in the neck area and/or to headaches.
Further positioning systems for transcranial magnetic stimulation are known from U.S. Pat. Nos. 6,926,660; 7,651,459; 8,088,058; and U.S. Patent Application publications 2010/0113959, 2015/0202453, and 2016/0030762; and from European patent EP2252367.